selecting one sweatshirt from a choice of five sweatshirts and one pair of pants from a choice of four pairs of pants

There are a total of 20 possible combinations of one sweatshirt and one pair of pants.

To determine this, you multiply the number of choices for the sweatshirt (5) by the number of choices for the pants (4):

5 x 4 = 20

Therefore, there are 20 possible outfits to choose from when selecting one sweatshirt and one pair of pants from the given choices.